Inductor structure

ABSTRACT

An inductor structure comprising a substrate; a plurality of insulation layers on the substrate; a first spiral electric conductive coil positioned in the insulation layers to form an inductor having a first direction of magnetic field; a second spiral electric conductive coil positioned in the insulation layers to form an inductor having a second direction of magnetic field, in which, the two or more inductors are independently positioned in a same 3-D space and have a good integration.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an inductor, and more particularly, toan inductor structure made with integrated circuit technology.

2. Description of the Prior Art

An inductor is a passive electronic component that stores energy in theform of a magnetic field, and an inductor tends to resist any change inthe amount of current flowing through it. The inductor is usually usedwith capacitors in various wireless communications applications forproviding stable currents, switched phases, filtering and resonance. Inits simplest form, the inductor consists of a wire loop or coil. Theinductance is directly proportional to the number of turns, thethickness, the length, and the radius of the coil. The inductance alsodepends on the type of material around which the coil is wound. In asemiconductor manufacturing process, at least two metal layers withspecifically designed layout patterns and a plurality of via plugs forconnecting these two metal layers are used to form a wire loop, thusfabricating an inductor onto an integrated circuit chip. Recently, forobtaining an inductor with a smaller size, a three-dimensional inductoris produced to have an increased coil density.

Please refer to FIG. 1 showing a conventional schematic diagram oftwo-level spiral inductor 10. For saving chip area, as shown in FIG. 1,the inductor 10 is designed as two layered coils. The inductor 10 hastwo ends P1 and P2 and spirally circles a point C starting at the outerend P1 from an outer ring to an inner ring for a desired number ofloops, which is then connected to another layer by a via plug, andspirals from an inner ring to an outer ring finally connecting to theend P2. It deserves to be mentioned that current flowing in the twolayered coils is in the same direction which increases the mutualinductance of the inductor 10, that is, the current flows into the endP1 from the outer ring to the inner ring in a clockwise direction thenconnects to the second layer by the via plug, and similarly flowsclockwise from the inner ring to the outer ring to the end P2.

Please refer to FIG. 2 showing a turn with essential components in athree-dimensional inductor manufactured using a conventionalsemiconductor technology disclosed in U.S. Pat. No. 6,037,649. Thethree-dimensional inductor 20 is made on a substrate 21 and comprises aN-turn coil. Each turn comprises a first-level metal line (M1) having afirst end and a second end, a second-level metal line (M2) having afirst part and a second part, and a third-level metal line (M3) having afirst end and a second end which are isolated through the first, thesecond, and the third isolating layers. The adjacent levels of metallines may be connected through the via plugs (24 and 27) in theisolating layers. The integral coil of the three-dimensional inductor isaccomplished and extends along the direction of the magnetic field ofthe three-dimension inductor by connecting the second-level metal line(M2) in the Nth turn with the third-level metal line (M3) in the (N+1)thturn coil.

The inductor structures described above include only one inductorstructure in the entire structure space. Therefore, the research anddevelopment to improve the integration level for an inductor structureis still needed.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a three-dimensionalinductor structure in which three independent inductors are integratedinto a same space to achieve an excellent integration level.

Another object of the present invention is to provide an inductorstructure in which two independent inductors are integrated into a samespace to achieve an excellent integration level.

The three-dimensional inductor structure according to the presentinvention comprises a substrate; a plurality of insulation layers on thesubstrate; a first spiral conductive coil disposed in the insulationlayer to form an inductor generating a magnetic field in a firstdirection; a second spiral conductive coil disposed in the insulationlayer to form an inductor generating a magnetic field in a seconddirection; and a third spiral conductive coil disposed in the insulationlayer to form an inductor generating a magnetic field in a thirddirection.

The inductor structure according to the present invention comprises asubstrate; a plurality of insulation layers on the substrate; a firstspiral conductive coil disposed in the insulation layer to form aninductor generating a magnetic field in a first direction; and a secondspiral conductive coil disposed in the insulation layer to form aninductor generating a magnetic field in a second direction, wherein thefirst direction and the second direction are not parallel.

In the inductor structure according to the present invention, two,three, or more coils are disposed respectively in a same space indifferent directions to give the inductor structure a relatively highintegration level. Therefore, only a relatively small space is needed toobtain a desired inductance.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a conventional two-level spiralinductor.

FIG. 2 shows a schematic diagram of a turn with necessary components ina conventional three-dimensional inductor coil.

FIGS. 3 to 5 shows respectively a schematic diagram of one of threecoils in a three-dimensional inductor structure of an embodimentaccording to the present invention.

FIG. 6A through FIG. 6D show a schematic diagram of a three-dimensionalinductor structure of an embodiment according to the present inventionand the detailed views of the inductor structure.

FIGS. 7-14 shows schematic diagrams of inductor structures of someembodiments according to the present invention.

DETAILED DESCRIPTION

The three-dimensional inductor structure according to the presentinvention comprises three coils disposed in a plurality of insulationlayers in a 3-D space. Each coil comprises a plurality of turns in aspiral type to form an inductor having an magnetic field with adirection. The three coils can be placed such that the conductive linesare in crossover positions. Alternatively, the three coils can bedisposed in the three separated parts of the space. Please refer toFIGS. 3 to 5 showing an embodiment of the three-dimensional inductorstructure according to the present invention. Only one coil is shown inthe drawing for a purpose of illustration. Three coils are substantiallyconstructed on a substrate in a same space.

Refer to FIG. 3 showing a coil of the three-dimensional inductorstructure according to the present invention. The coil is a first spiralconductive coil 30 disposed in, for example, nine insulation layers. Thefirst spiral conductive coil 30 comprises a plurality of turns, and eachturn comprises four conductive sections. The first conductive section 32is disposed on the ninth layer, being the top layer, of the nineinsulation layers. The second conductive section 34 is disposed in thefirst layer, being the bottom layer, of the nine insulation layers. Thetwo conductive sections 32 and 34 are electrically connected through thethird conductive section 36. The third conductive section 36 is formedby connecting a via plug in each insulation layer between the first andthe ninth insulation layers. The third conductive section 36 connectsthe first end 33 of the first conductive section 32 and a first end 35of the second conductive section 34. The fourth conductive section 38 isformed by connecting another via plug in each insulation layer betweenthe first and the ninth insulation layers. The fourth conductive section38 connects the second end 37 of the second conductive section 34 andthe second end 39 of the first conductive section 32 of an adjacentanother turn. A turn is thus formed In such a way, and the same turnstructure is duplicated to form a number of turns in the insulationlayers to obtain a spiral coil disposed in the nine insulation layers.When an electric current flows through the coil, an induced magneticfield occurs in the direction of x coordinate.

Refer to FIG. 4 showing another coil of the three-dimensional inductorstructure according to the present invention. The coil is a secondspiral conductive coil 40 disposed in, for example, seven insulationlayers in the middle part of the nine insulation layers mentioned above,that is, the second to the eighth layers. The first spiral conductivecoil 40 comprises a plurality of turns, and each turn comprises fourconductive sections. The fifth conductive section 42 is disposed in theeighth layer of the nine insulation layers. The sixth conductive section44 is disposed in the second layer of the nine insulation layers. Thetwo conductive sections 42 and 44 are electrically connected through theseventh conductive section 46. The seventh conductive section 46 isformed by connecting a via plug in each insulation layer between thesecond and the eighth insulation layers, to connect the first end 43 ofthe fifth conductive section 42 and a first end 45 of the six conductivesection 44. The eighth conductive section 48 is formed by connectinganother via plug in each insulation layer between the second and theeighth insulation layers to connect the second end 47 of the sixthconductive section 44 and the second end 49 of the fifth conductivesection 42 of an adjacent another turn. A turn is thus formed In such away, and the same turn structure is duplicated to form a number of turnsin the insulation layers to obtain a spiral coil disposed in the seveninsulation layers. When an electric current flows through the coil, aninduced magnetic field occurs in the direction of y coordinate. In suchstructure, some conductive sections of the second spiral conductive coil40 and some conductive sections of the first spiral conductive coil usesame insulation layers but are crossover each other since the conductivesections are located in different parts of the same insulation layers.

Refer to FIG. 5 showing still another coil of the three-dimensionalinductor structure according to the present invention. The coil is athird spiral conductive coil 50 disposed in, for example, fiveinsulation layers in the middle part of the nine insulation layersmentioned above, that is, the third to the seven layers. The firstspiral conductive coil 50 comprises a plurality of turns. One turn 52 ora plurality of turns in a flat spiral type are disposed in one of theinsulation layers. The turns in the adjacent insulation layers connectto each other through a via plug 56 in the insulation layer. A turn isthus formed in such a way, and the same turn structure is duplicated toform a number of turns in the insulation layers to obtain a spiral coildisposed in the five insulation layers of the nine insulation layers.When an electric current flows through the coil, an induced magneticfield occurs in the direction of z coordinate. In such structure, someconductive sections of the third spiral conductive coil 50 and someconductive sections of the first or the second spiral conductive coiluse same insulation layers but are crossover each other since theconductive sections are located in different parts of the sameinsulation layers.

The three-dimensional inductor structure obtained as described above maybe shown as the schematic diagram in FIG. 6A and the detailed views ofthe inductor structure, FIGS. 6C-6D. The coils 60, 62, and 64 aredisposed in a same 3-D space and cross over to each other. The arrowsshow some examples of flow direction for electric current in FIG. 6A.When two inductors are formed from coils each having a magnetic fieldwith a direction perpendicular to each other, interference will notoccur between the two inductors. The three-dimensional inductorstructure according to the present invention may have many embodiments.For example, the coil 60 may be disposed in the first layer to the ninthlayer of the insulation layer as shown in FIG. 6B, and the coil 62 maybe disposed in the second layer to the eighth layer of the insulationlayers as shown in FIG. 6C. One or more insulation layers may be furtherformed between the first layer and the second layer or between the ninthlayer and the eighth layer. Alternatively, the coil 62 may be disposedin the first layer to the ninth layer of the insulation layer, and thecoil 60 may be disposed in the second layer to the eighth layer of theinsulation layers. One or more insulation layers may be further formedbetween the first layer and the second layer or between the ninth layerand the eighth layer. The coil 64 may be disposed in the third layer tothe seventh layer of the insulation layers as shown in FIG. 6D. The coil64 may be disposed in more or less than five insulation layers, evenonly in one layer, and thus the entire structure may only have fivelayers. When the coil 64 is disposed in only one insulation layer, itmay be formed in a flat spiral shape. Alternatively, the coil 64 isdisposed in more than five insulation layers and the entire structurehas more than nine insulation layers. Alternatively, two adjacent turnsof the coil 64 may have an interval with several insulation layers, andthe coils 60 and 62 are disposed in the several insulation layers.Therefore, the three-dimensional inductor structure according to thepresent invention may have a structure of only five or more insulationlayers without limit, depending on desired designs.

Alternatively, in another aspect according to the present invention, theinductor structure may comprise two coils having structures as two ofthe coils 60, 62, and 64, for example, coils 60 and 62, coils 60 and 64,or coils 60 and 64, occupying a same space. The current directions ofthe coils may be in a variety of combinations.

The spiral coils described above are disposed in a same space, togetherusing the insulation layers and crossing over to each other. The coilsmay be also disposed in different parts of the 3D-space, that is, thethree coils do not occupy the insulation layers in common, as shown inFIG. 7 showing a schematic diagram of another embodiment of thethree-dimensional inductor structure according to the present invention.The coil 70 is disposed in the first part of the insulation layers asdescribed for the first spiral conductive coil 30, provided that thecoil 70 is singly disposed in this part of the nine insulation layers.When an electric current flows through the coil, an induced magneticfield occurs in the direction of x coordinate. The coil 72 is disposedin the second part of the insulation layers as described for the secondspiral conductive coil 40, provided that the coil 72 is singly disposedin this part of the nine insulation layers. When an electric currentflows through the coil, an induced magnetic field occurs in thedirection of y coordinate. The coil 74 is disposed in the third part ofthe insulation layers as described for the third spiral conductive coil50, provided that the coil 74 is singly disposed in this part of thenine insulation layers. When an electric current flows through the coil,an induced magnetic field occurs in the direction of z coordinate. Therelative positions and the current directions for the coils 70, 72, and74 in the three-dimensional inductor structure according to the presentinvention, as shown in FIG. 7, may have other combinations, such as, thecoil 70 between the coil 72 and the coil 74, the coil 74 between thecoil 70 and the coil 72, and the like. Alternatively, as shown in FIG.11, the coils 70, 72, and 74 may be in a vertical arrangement in theinsulation layers. The relative positions and current directions may bein other combinations, for example, the coil 70 between the coil 72 andthe coil 74, the coil 74 between the coil 70 and the coil 72, and thelike.

The three-dimensional inductor structure according to the presentinvention disposed in one space may comprise one coil separatelydisposed in one part of the space and another two coils disposedtogether and crossing over to each other in another part of the space.For example, a first coil and a second coil together use a part of thenine insulation layers, and a third coil singly uses the rest of thenine insulation layers. Alternatively, a first coil and a third coiltogether use a part of the nine insulation layers, and the other coilsingly uses the rest of the nine insulation layers.

Alternatively, in another aspect according to the present invention, theinductor structure may comprise two coils having structures as two ofthe coils 70, 72, and 74, for example, the coils 70 and 72, the coils 72and 74, or the coils 70 and 74, occupying different parts of theinsulation layers. The current directions of the coils may be in avariety of combinations, and the directions of the magnetic fieldsproduced from the two coils are not parallel from each other. FIGS. 8 to10 each show the inductor structure comprising the coils 70 and 72, thecoils 72 and 74, and the coils 70 and 74, respectively, in a lateralarrangement in the insulation layers. FIGS. 12 to 14 each show theinductor structure comprising the coils 74 and 72, the coils 72 and 70,and the coils 74 and 70, respectively, in a vertical arrangement,occupying different insulation layers.

The three-dimensional inductor structure according to the presentinvention may be disposed on the substrate, such as a semiconductorsubstrate or silicon substrate, and manufactured by semiconductormanufacturing processes, such as deposition, etching, chemicallymechanical planarization, copper damascene, and metal via plug process.The insulation layer may comprise electrically insulation material, suchas silicon dioxide (SiO₂), silicon nitride (Si₃N₄), phosphosilicateglass (PSG), or borophosphosilicate glass (BPSG). The conductivesections and via plugs may comprise electrically conductive material,such as metal. The metal may be for example copper or copper-aluminumalloy. The shape of each coil including conductive sections and viaplugs and the positions for via plug connection are not speciallylimited and can be designed as desired.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A three-dimensional inductor structure, comprising: a substrate; aplurality of insulation layers on the substrate; a first spiralconductive coil disposed in the insulation layers to form an inductorgenerating a magnetic field in a first direction; a second spiralconductive coil disposed in the insulation layers to form an inductorgenerating a magnetic field in a second direction; and a third spiralconductive coil disposed in the insulation layers to form an inductorgenerating a magnetic field in a third direction, wherein, a conductivesection of the first spiral conductive coil, a conductive section of thesecond spiral conductive coil, and a conductive section of the thirdspiral conductive coil are disposed in a same one of the insulationlayers and cross over to each other.
 2. A three-dimensional inductorstructure comprising: a substrate; a plurality of insulation layers onthe substrate; a first spiral conductive coil disposed in the insulationlayers to form an inductor generating a magnetic field in a firstdirection; a second spiral conductive coil disposed in the insulationlayers to form an inductor generating a magnetic field in a seconddirection; and a third spiral conductive coil disposed in the insulationlayers to form an inductor generating a magnetic field in a thirddirection, wherein the first spiral conductive coil, the second spiralconductive coil, and the third spiral conductive coil occupy theinsulation layers in common; and the first spiral conductive coil has aplurality of first turns and each of the first turns comprises: a firstconductive section in a first insulation layer being the top layer ofthe insulation layers; a second conductive section in a secondinsulation layer being the bottom layer of the insulation layers; athird conductive section comprising a first group of via plugs formed inthe insulation layers to connect a first end of the first conductivesection and a first end of the second conductive section; and a fourthconductive section comprising a second group of via plugs formed in theinsulation layers to connect a second end of the second conductivesection and a second end of the first conductive section of an adjacentanother first turn.
 3. The three-dimensional inductor structure asclaimed in claim 2, wherein the second spiral conductive coil has aplurality of second turns and each of the second turns comprises: afifth conductive section in a third insulation layer under the firstinsulation layer; a sixth conductive section in a fourth insulationlayer above the second insulation layer; a seventh conductive sectioncomprising a third group of via plugs formed in the insulation layers toconnect a first end of the fifth conductive section and a first end ofthe sixth conductive section; and an eighth conductive sectioncomprising a fourth group of via plugs formed in the insulation layersto connect a second end of the sixth conductive section and a second endof the fifth conductive section of an adjacent another second turn. 4.The three-dimensional inductor structure as claimed in claim 3, whereinthe third spiral conductive coil has a plurality of third turns eachdisposed in an insulation layer, respectively, under the thirdinsulation layer and above the fourth insulation layer, and two adjacentthird turns connect each other through a via plug in the insulationlayer.
 5. The three-dimensional inductor structure as claimed in claim2, wherein the substrate comprises silicon.
 6. The three-dimensionalinductor structure as claimed in claim 2, wherein the first, second, andthird spiral conductive coils comprise metal.
 7. The three-dimensionalinductor structure as claimed in claim 2, wherein the first direction isperpendicular to the second direction.